This invention relates to an apparatus and method for monitoring corrosion occurring in the pipelines and other metallic structures due to a corrosive medium in contact with such structure, and more particularly to an electrical resistance probe for determining corrosion by measuring the change in resistance in electrical resistance elements exposed to such corrosive medium.
U.S. Pat. No. 3,104,355 to Holmes et al discloses, inter alia, an electrical resistance corrosion measuring probe compensated for temperature variations in the corrosive medium by employing two resistance elements of similar material which are both completely exposed to the corrosive medium. One of these elements has a materially larger cross-section than the other so that its resistance changes with corrosion at a measurably different proportional rate than the change occurring in the other element. By connecting the two elements in opposite sides of the galvanometer type measurement bridge circuit, resistance readings may be made. Corrosion of the elements is measured by resistance readings taken either continuously (as by reading resistance variation) or at selected intervals.
The above described probe of Holmes suffers from the disadvantage that one of the exposed resistance elements has a cross-sectional area which is much larger than the other and therefore has a negligible resistance change due to corrosion.
It is an object of this invention to provide an electrical resistance corrosion measuring probe having an excellent thermal response while avoiding the above noted disadvantage of the Holmes et al probe. It is a further object of this invention to provide a probe of this type which allows the use of a complementary measuring bridge circuit in its most sensitive region.
Other objects, features and advantages of the present invention will be apparent from the following description.